My ati radeon 6870 was working well in my mac pro 2008. I decided with everything working smoothly in both OS X ML 10.8.2 and in Win 7, to go ahead and use cindori's 6870 package to get the dvdplayer working in OSX. I made the mistake of installing the ATIgraphicsupdate rather than just installing the ATY_init.Kext file. Now the graphics card does not work with OS-X at all. It still works fine in windows 7, but it is simply black when i attempt to use OS-X. Its not just the bootscreen, but the login screen is black as well. The only thing that works is the disk utility screen from cmd +R. I'm not sure what to do. I did a restore install of mountain lion from the recovery partition, but it did not solve the issue. I'm now going to do a clean install. If anyone knows how i can resolve this, please let me know.